MAX9141ESA-T Maxim Integrated Products, MAX9141ESA-T Datasheet - Page 7

• Manufacturer Part Number: MAX9141ESA-T
• Description: Comparator ICs 40ns, Single, Low-Po wer + SHDN & LE, 3V-
• Manufacturer: Maxim Integrated Products

The MAX9140/MAX9141/MAX9142/MAX9144 single-
supply comparators feature internal hysteresis, high
speed, and low power. Their outputs are pulled to with-
in 300mV of either supply rail without external pullup or
pulldown circuitry. Rail-to-rail input voltage range and
low-voltage single-supply operation make these
devices ideal for portable equipment. The
MAX9140/MAX9141/MAX9142/MAX9144 interface
directly to CMOS and TTL logic.
Most high-speed comparators oscillate in the linear
region because of noise or undesired parasitic feed-
back. This tends to occur when the voltage on one
input is at or equal to the voltage on the other input. To
counter the parasitic effects and noise, the MAX9140/
MAX9141/MAX9142/MAX9144 have an internal hystere-
sis of 1.5mV.
The hysteresis in a comparator creates two trip points:
one for the rising input voltage and one for the falling
input voltage (Figure 1). The difference between the trip
points is the hysteresis. The average of the trip points is
the offset voltage. When the comparator’s input volt-
ages are equal, the hysteresis effectively causes one
comparator input voltage to move quickly past the
other, thus taking the input out of the region where
oscillation occurs. Standard comparators require hys-
teresis to be added with external resistors. The
MAX9140/MAX9141/MAX9142/MAX9144’s fixed internal
hysteresis eliminates these resistors. To increase hys-
teresis and noise margin even more, add positive feed-
back with two resistors as a voltage divider from the
output to the noninverting input.
Figure 1 illustrates the case where IN- is fixed and IN+
is varied. If the inputs were reversed, the figure would
look the same, except the output would be inverted.
The MAX9141 includes an internal latch that allows
storage of comparison results. The L
input impedance. If L
(i.e., the comparator operates as though the latch is not
present). The comparator's output state is latched
when L
The MAX9141 shuts down when the
When shut down, the supply current drops to less than
12µA, and the three-state output becomes high imped-
ance. The
Connect
down with
output will be indeterminate.
—
E is pulled low (Figure 2).
S
—
H
—
L
—
–
D
S
—
—
E
N
Shutdown Mode (MAX9141 Only)
H
–
—
high (transparent state); otherwise, the
D
—
to V
N
–
_______________________________________________________________________________________
pin has a high-input impedance.
CC
—
E is high, the latch is transparent
Detailed Description
for normal operation. Exit shut-
40ns, Low-Power, 3V/5V, Rail-to-Rail
—
E pin has a high
–
S
—
H
—
D
—
N
–
pin is low.
Single-Supply Comparators
The MAX9140/MAX9141/MAX9142/MAX9144 include
internal protection circuitry that prevents damage to the
precision input stage from large differential input volt-
ages. This protection circuitry consists of two back-to-
back diodes between IN+ and IN- as well as two series
4.1kΩ resistors (Figure 3). The diodes limit the differen-
tial voltage applied to the internal circuitry of the com-
parators to be no more than 2V
ward voltage drop of the diode (about 0.7V at +25°C).
For a large differential input voltage (exceeding 2V
this protection circuitry increases the input bias current
at IN+ (source) and IN- (sink).
Input current with large differential input voltages
should not be confused with input bias current (I
long as the differential input voltage is less than 2V
this input current is equal to I
rect logic state if one or both inputs are within the com-
mon-mode range.
Figure 1. Input and Output Waveform, Noninverting Input
Varied
V
V
V
COMPARATOR
TRIP+
HYST
TRIP-
OUTPUT
Input Current =
(IN+ - IN-) - 2V
Input Stage Circuitry
2 x 4.1kΩ
B
. The output is in the cor-
F
, where V
V
IN+
V
V
F
OS
IN-
=
= 0
F
V
TRIP+
V
V
is the for-
OH
OL
2
+ V
B
TRIP-
). As
F
F
7
),
,